Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$128.73	8.381%	$139.5189	$139.52	$139.50	$139.50
Purchase #2	$62.43	11.796%	$69.7942	$69.79	$69.80	$69.80
Purchase #3	$235.78	6.351%	$250.7544	$250.75	$250.75	$250.80
Purchase #4	$191.28	4.498%	$199.8838	$199.88	$199.90	$199.90
Purchase #5	$91.67	13.207%	$103.7769	$103.78	$103.80	$103.80
Purchase #6	$244.30	5.160%	$256.9059	$256.91	$256.90	$256.90
Purchase #7	$120.30	9.255%	$131.4338	$131.43	$131.45	$131.40
7 purchase totals =	$1,074.49		$1,152.0679	$1,152.06	$1,152.10	$1,152.10